1. Field of the Invention
This invention relates to an image forming toner, 2-component developer, image forming method and method for manufacturing image forming toner for electronic photography devices, and more particular to the image forming toner, 2-component developer, image forming method and method for manufacturing image forming toner that is suitable for application in an image forming apparatus with a high temperature fixing.
2. Related Arts
In recent years, image forming apparatus that uses electronic photography technique are used as computer output devices. In this kind of image forming apparatus, high speed processing is desired. Therefore, image forming toner that is suitable for high-speed printing is also desired.
A typical electronic photography method for image forming apparatus comprises the following steps: The photosensitive body is charged and then exposed by light image, thereby a latent image is formed on the photosensitive body. Developer is supplied to the photosensitive body and the latent image is developed, and then the toner image is transferred to the medium. Then the toner is fixed to the medium.
A heat rolling method or oven method that heats the toner directly by a roller or the like, and a flash fixing method that performs fixation by light irradiation or extreme infrared radiation are widely used as the method for fixing the toner.
In the heat rolling method, the toner is fixed by bringing a high-temperature roller in contact with the toner and heating and applying pressure it directly. Therefore, it is possible to make an inexpensive fixation mechanism. On the other hand, it has disadvantages in that the paper has a tendency to roll easily after fixation, the paper may become dirty due to offset when the fixation roller becomes dirty from the toner, high-speed printing becomes difficult and fixing toner to seals and post cards is difficult when the paper rolls.
In the flash fixation method there is no direct contact so it has advantages in that the paper is not rolled after fixation, there is no offset, high-speed printing is possible, and it is easy to fix toner to seals and postcards. Therefore, flash fixation is used in high-speed printers and copiers.
In high-speed fixation methods such as flash fixation, a large quantity of energy is applied to the sheet instantaneously, and the temperature of the most top surface of the printing toner reaches 300xc2x0 C. or more. Therefore, sublimation of the binder resin component of the toner occurs. Gas and odors are produced by this sublimation.
The toner binder for flash fixation must instantly raise the temperature of the toner to make it soft and melt, so toner with different properties than the toner for the heat-roller fixation method is desired. In other words, a material with a high decomposition temperature is used. A toner whose main component is a polyester resin is used as the binder for this flash fixation toner. Also, in order to reduce the gas and odor produced by the aforementioned sublimation, it is proposed that the mean molecular weight of the polyester resin should be between 10,000 and 50,000 (for example as disclosed in Japanese unexamined published patent No. H5-107805).
Ultra-high-speed printing is desired in this kind of image formation apparatus. For example, the capability of printing 100 sheets or more per minute is desired. When forming images at ultra high speed, the fixation speed is also increased, and the sublimation matter of the toner binder increases. In order to prevent that this sublimate is directly discharged to the air, so a dust collection system using highly efficient smoke filters is installed in the printer.
However, with conventional toner, the smoke filter quickly becomes clogged with the sublimate. Therefore, in a high-speed printer, there is the problem that the replacement period of the filter is shortened.
The objective of this invention is to provide image forming toner, 2-component developer, an image forming method and method for manufacturing image forming toner for image forming devices for preventing early clogging of a filter even when performing high-speed image formation.
Another objective of this invention is to provide image forming toner, 2-component developer, an image forming method and method for manufacturing image forming toner for image forming devices for reducing odors during fixation.
A further objective of this invention is to provide image forming toner, 2-component developer, an image forming method and method for manufacturing image forming toner for image forming devices for lengthening the life of the filter and improving the quality of fixation.
Yet a further objective of this invention is to provide image forming toner, 2-component developer, an image forming method and method for manufacturing image forming toner for image forming devices for lengthening the life of the filter and making stable developing possible.
A toner for image formation of this invention comprises at least a binder resin and colorant and where the ratio of the 500 to 1000 molecular weight components of the toner, measured by gel permeation chromatography, is 10 parts by weight or less with respect to 100 parts by weight of the entire toner.
The inventors analyzed the components clogging the filter in order to gain a better understanding of the clogging of the filter due to sublimation of the toner binder. To do this, the structure and mass of the clogging components were analyzed by a nuclear magnetic harmonic spectrogram. As a result, the following was found:
First, the sublimate component in flash fixation is a monomer component mainly made up of a bisphenol-A-alkylene oxide additive with molecular weight of 500 or less, or dimer or trimer comprising a bisphenol-A-alkylene oxide additive with molecular weight between 500 to 1000 and phthalic acid or trimellitic acid.
Second, components with a molecular weight of 500 to 1000 are found largely on the top layer of the filter while components with a molecular weight of 500 or less are found largely on the bottom layer of the filter. Moreover, since the monomer component with a molecular weight of 500 has a small molecular weight, it reaches the bottom layer of the filter, whereas the sublimate component with a molecular weight of 500 to 1000 becomes hardened on the surface layer of the filter and becomes the major cause of clogging of the filter.
Therefore, in order to reduce clogging of the filter and to lengthen its life, it is important to reduce the total weight of the 500 to 1000 molecular weight component in the toner. As a result of diligent investigation and research, it was found that when the ratio of the toner components having a molecular weight of 500 to 1000, is 10 parts by weight or less with respect to 100 parts by weight of the entire toner, then it is possible to lengthen the life of the filter. It is even more desirable for the ratio to be 5 parts by weight or less. It is desirable that the lower limit of the components having a molecular weight of 500 to 1000 be as near to zero as possible.
In another feature of the invention, the ratio of the toner component having molecular weight of 500 or less that is measured by gel permeation chromatography, is less than 4 parts by weight with respect to the 100 parts by weight of the entire toner.
From the results of the analysis it was found that since the monomer component with molecular weight of 500 or less is a small molecular weight, it passes through the filter and becomes the cause of odor. This monomer component can be recovered somewhat by the activated charcoal of the filter, however, this component must also be reduced from the toner.
Therefore, in this invention, the odor is reduced by making the ratio of the toner component with molecular weight of 500 or less 4 parts by weight or less with respect to the 100 parts by weight of the entire toner.
In another feature of the invention, the binder resin comprises at least a polyester resin consisted of the bisphenol-A-alkylene oxide additive expressed by the chemical formula 1 given below. 
(In the formula, R is an ethylene or propylene base, and x and y are both integers equal to 1 or more.)
Polyester resin is used for the binder resin so it is possible to prevent decomposition of the binder even when the fixation temperature is high as in the case of flash fixation.
In another feature of the invention, x and y in the formula for the bisphenol-A-alkylene oxide additive are 1, and R is an ethylene-based compound making up 60 mole % or more of the polyester alcohol component.
With x and y in the formula for the bisphenol-A-alkylene oxide additive equal to 1, and R as a ethylene-based compound, reactivity is high and it is possible to reduced the monomer, and dimer or trimer components remaining in the polyester. By doing this, it is possible to prevent clogging of the filter, as well as to reduce odors.
In another feature of the invention, 0.01 to 10 parts by weight of the compound given by the chemical formula 2 below is added.
[Chemical Formula 2]
Cxe2x80x94[CH2xe2x80x94Oxe2x80x94COxe2x80x94(CH2)nxe2x80x94CH3]4 n=14 or more 
This makes it possible to improve flash fixation as well as makes it possible to prevent printing defects called void. Furthermore, it is preferred when the added weight is 0.5 to 5 parts by weight.
In another feature of the invention, a polypropylene compound with an mean molecular weight of 10,000 or more is added. By adding the polypropylene compound, it is possible to improve the pulverization characteristics of the toner. Furthermore, since the mean molecular weight of the polypropylene compound is greater than 10,000, it is possible to prevent any effects from it on clogging of the filter.
In another feature of the invention, the toner is toner used in flash fixation. Since the toner is used in flash fixation, it is possible to reduce clogging of the filter and odors due to sublimation of the binder during flash fixation.
The 2-component developer of this invention, comprises toner and a carrier, in which the ratio of the component of the toner determined by gel permeation chromatography to have molecular weight of 500 to 1000 is less than 10 parts by weight with respect to the 100 parts by weight of the entire toner, and a carrier that has an average particle diameter of 30 to 100 xcexcm.
This makes it possible to prevent clogging of the filter, as well as makes it possible to supply a 2-component developer with a long life.
The image forming method of this invention comprises: a step of forming a toner image on a medium by using a toner in which the ratio of the component of the toner determined by gel permeation chromatography to have molecular weight of 500 to 1000 is less than 10 parts by weight with respect to the 100 parts by weight of the entire toner; and a step of performing flash fixation of the toner on the medium.
This makes it possible to prevent clogging of the filter even when performing flash fixation.
The method of manufacturing toner for image formation of this invention comprises: a step of creating a polyester binder; a step of washing the created polyester binder with alcohol; and a step of mixing the polyester binder, that has been washed with alcohol, with a colorant to create the toner.
Alcohol does not melt the high-molecular-weight polyester, however the monomer and dimer are dissolved in alcohol. Therefore, by washing the polyester binder with alcohol, it is possible to greatly reduce the monomer or dimer that causes clogging of the filter and odors.
Other features and advantages of the present invention will become readily apparent from the following description taken in conjunction with the accompanying drawings.